Constraining the Secluded and Catalyzed Annihilation Dark Matter with Fermi-LAT and Planck Data

Abstract: We propose a dark matter (DM) model with a complex scalar charged under a hidden gauge symmetry, denoted as $U(1)D$. The scalar field is the DM candidate while the $U(1)_D$ gauge field $A'$ plays the role of a mediator, which connects the dark sector to the standard model (SM) sector via a tiny kinetic mixing. We find that both the secluded and catalyzed annihilation scenarios can be realized in this model. The phenomenology of DM, including relic density, indirect detection (Fermi-LAT), and CMB (Planck) constraints, is discussed. We also extend our discussion to DM with other spins, including Dirac fermion and vector boson. Our analysis is carried out in two models, denoted as $U(1)_D \times U(1)_Y$ and $U(1)_D \times U(1){L_\mu-L_\tau}$, with the former corresponding to $A'$ kinetically mixing with the $U(1)Y$ gauge field $B$ and the latter corresponding to $A'$ mixing with the $U(1){L_\mu-L_\tau}$ gauge field $Z'$. We find that, in previous studies, the indirect detection limits were overly restrictive because they only considered the simplified $2\mathrm{DM} \to 2\mathrm{SM}$ annihilation channel. In contrast, by performing a complete calculation of the gamma-ray and CMB constraints from the process $2\mathrm{DM} \to 2A' \to 4\mathrm{SM}$ in the models we consider, we observe weaker constraints in both the $U(1)D \times U(1)_Y$ and $U(1)_D \times U(1){L_\mu-L_\tau}$ models, with the $U(1)D \times U(1){L_\mu-L_\tau}$ model being subject to the weakest constraints overall since it involves less hadronic decay processes.